Combating pests with fluorine-substituted 2,2,3,3-tetramethylcyclopropane-1-carboxylic acid benzyl esters

ABSTRACT

2,2,3,3-Tetramethylcyclopropanecarboxylic acid fluorine-substituted-benzyl esters of the formula ##STR1## in which R 1  is hydrogen, cyano, or alkyl, alkenyl or alkynyl each with up to 4 carbon atoms, and 
     R 2  is a phenyl radical which is substituted by halogen and/or by optionally halogen-substituted phenoxy, with the proviso that the radical R 2  in total contains at least one fluorine substituent, 
     which possess insecticidal and acaricidal properties.

The invention relates to certain new fluorine-substituted 2,2,3,3-tetramethyl-cyclopropane-1-carboxylic acid benzyl esters, to a process for their preparation and to their use as agents for combating pests, especially as insecticides and acaricides.

It is known that certain cyclopropanecarboxylic acid esters, for example 3-(2-methyl-prop-1-en-1yl)-2,2-dimethyl-cyclopropane-1-carboxylic acid 3-phenoxy-benzyl ester, 3-(2,2-dichloro-vinyl)-2,2-dimethyl-cyclopropane-1-carboxylic acid 3-phenoxy-benzyl ester, 2,2,3,3-tetramethyl-cyclopropane-1-carboxylic acid 3-phenoxy-benzyl ester and 2,2,3,3-tetramethyl-cyclopropane-1-carboxylic acid 3-phenoxy-α-cyano-benzyl ester, have an insecticidal action (see British patent specification Nos. 1,243,858 and 1,413,491 and U.S. Pat. No. 3,835,176). However, the action of these compounds is not always satisfactory, especially in the case of low concentrations of active compound and when small amounts are used.

The present invention now provides, as new compounds, the fluorine-substituted 2,2,3,3-tetramethyl-cyclopropane-1-carboxylic acid benzyl esters of the general formula ##STR2## in which

R¹ represents hydrogen, cyano or alkyl, alkenyl or alkynyl with in each case up to 4 carbon atoms, and

R² represents a phenyl radical which is substituted by halogen and/or by optionally halogen-substituted phenoxy, with the proviso that the radical R² in total contains at least one fluorine substituent.

Surprisingly, the compounds of the formula (I) according to the invention exhibit a considerably more powerful insecticidal and acaricidal action than the compounds of analogous structure and the same type of action which are known from the state of the art.

The general formula (I) includes the various possible optically active isomers and mixtures thereof.

Preferred compounds of the formula (I) are those in which

R¹ represents hydrogen or cyano and

R² represents pentafluorophenyl, 4-fluoro-3-phenoxy-phenyl, 3-(4-fluoro-phenoxy)-phenyl or 4-fluoro-3-(4-fluoro-phenoxy)-phenyl.

The invention also provides a process for the preparation of a compound of the formula (I) in which 2,2,3,3-tetramethyl-cyclopropane-1-carboxylic acid of the formula ##STR3## or a reactive derivative thereof, is reacted with an alcohol of the general formula ##STR4## in which R¹ and R² have the meanings indicated above, or with a reactive derivative thereof, if appropriate in the presence of an acid acceptor and/or a catalyst and if appropriate using a diluent.

In a preferred variant (a) of the preparative process for the compounds of the formula (I), 2,2,3,3-tetramethyl-cyclopropane-1-carboxylic acid chloride of the formula ##STR5## is reacted with a benzyl alcohol of the formula (III) above, in the presence of an acid acceptor and using a diluent.

In a further preferred process variant (b), in particular for the preparation of a compound of the formula (I) in which R¹ represents cyano and R² represents fluorine-substituted phenoxy-phenyl, the acid chloride of the formula (IIa) above is reacted with an appropriate phenoxy-benzaldehyde of the general formula

    OHC--R.sup.2                                               (IV),

in which R² represents fluorine-substituted phenoxyphenyl, and at least an equimolar amount of an alkali metal cyanide (preferably sodium cyanide or potassium cyanide) in the presence of water and a water-immiscible organic solvent and if appropriate in the presence of a catalyst.

Other reactive derivatives of the carboxylic acid of the formula (II) which may be mentioned are lower alkyl esters thereof, which can be reacted with alcohols of the formula (III) by customary methods.

It is also possible to react alkali metal salts, alkaline earth metal salts or ammonium salts of the carboxylic acid (II) with benzyl halides which are derived from the benzyl alcohols of the formula (III) to give compounds of the formula (I).

If, for example, pentafluorobenzyl alcohol is used as the starting substance in process variant (a) and 4-fluoro-3-(4-fluoro-phenoxy)-benzaldehyde is used as the starting substance in variant (b), the reactions in the two process variants can be illustrated by the following equations: ##STR6##

The 2,2,3,3-tetramethyl-cyclopropane-1-carboxylic acid to be used as the starting compound is already known (see U.S. Pat. No. 3,835,176).

The acid chloride of the formula (IIa) can be obtained from the above acid in the customary manner, for example by reaction with thionyl chloride, if appropriate in the presence of a diluent, for example carbon tetrachloride, at temperatures between 10° and 100° C.

Formula (III) provides a definition of the benzyl alcohols also to be used as starting substances. Preferably, in this formula, R¹ and R² have those meanings which have already been mentioned as preferred in the definition of R¹ and R² in formula (I).

Examples of the starting compounds of the formula (III) which may be mentioned are: pentafluorobenzyl alcohol, 4-fluoro-3-phenoxy-benzyl alcohol, 3-(4-fluoro-phenoxy)-benzyl alcohol, 4-fluoro-3-(4-fluoro-phenoxy)-benzyl alcohol and 3-(4-fluoro-phenoxy)-α-cyano-benzyl alcohol.

The starting compounds of the formula (III) are already known (see British patent specification No. 1,078,511 and DE-Os's (German Published Specifications) Nos. 2,621,433, 2,709,264 and 2,739,854).

Formula (IV) provides a definition of the phenoxybenzaldehydes which can be used as starting substances. Preferably, in this formula, R² has those meanings which have already been mentioned as preferred in the definition of R² in formula (I). Examples of the starting substances which may be mentioned are: 4-fluoro-3-phenoxybenzaldehyde, 3-(4-fluoro-phenoxy)-benzaldehyde and 4-fluoro-3-(4-fluoro-phenoxy)-benzaldehyde.

The phenoxybenzaldehydes of the formula (IV) are already known (see DE-OS's (German Published Specifications) Nos. 2,621,433, 2,709,264 and 2,739,854).

All the variants of the process for the preparation of the compounds of the formula (I) are preferably carried out using a diluent. Possible diluents are virtually any of the inert organic solvents. These include, as preferences, aliphatic and aromatic, optionally halogenated hydrocarbons, such as pentane, hexane, heptane, cyclohexane, petroleum ether, benzine, ligroin, benzene, toluene, xylene, methylene chloride, ethylene chloride, chloroform, carbon tetrachloride, chlorobenzene and o-dichlorobenzene; ethers, such as diethyl ether, dibutyl ether, glycol dimethyl ether, diglycol dimethyl ether, tetrahydrofuran and dioxane; ketones, such as acetone, methyl ethyl ketone, methyl isopropyl ketone and methyl isobutyl ketone; esters, such as methyl acetate and ethyl acetate; nitriles, for example acetonitrile and propionitrile; amides, for example dimethylformamide, dimethylacetamide and N-methylpyrrolidone; and dimethylsulphoxide, tetramethylene sulphone and hexamethylphosphoric acid triamide.

Variant (a) of the process according to the invention is preferably carried out in the presence of an acid acceptor. The customary acid-binding agents can be used as the acid acceptors. Acid-binding agents which have proved particularly suitable are alkali metal carbonates and alkali metal alcoholates, such as sodium carbonate, potassium carbonate, sodium methylate or ethylate and potassium methylate or ethylate, and furthermore aliphatic, aromatic or heterocyclic amines, for example triethylamine, trimethylamine, dimethylaniline, dimethylbenzylamine, pyridine, diazabicyclooctane, diazabicyclononane and diazabicycloundecene.

Variant (b) of the process according to the invention is preferably carried out in the presence of water and one of the above-mentioned organic solvents which is not water-miscible. The above-mentioned hydrocarbons are particularly suitable for this variant.

Compounds which are suitable for the transfer of anions from water into organic solvents are preferably used as catalysts in process variant (b). Examples of such compounds are benzyl-triethyl-ammonium bisulphate, tetrabutylammonium bromide and methyl-trioctylammonium chloride (Aliquat 336).

The reaction temperature can be varied within a substantial range in all process variants. In general, the reaction is carried out between 0° and 100° C., preferably at from 10° to 50° C.

The process according to the invention is in general carried out under normal pressure. The starting substances are usually employed in equimolar amounts for carrying out the process according to the invention. An excess of one or the other of the reactants provides no significant advantages. The starting substances are brought together in suitable diluents and, if appropriate after adding an acid acceptor and/or a catalyst, stirring until the reaction has ended.

Working up can be carried out by customary methods, for example by a procedure in which the reaction mixture is diluted with water and/or a water-immiscible organic solvent, for example toluene, if appropriate, and the organic phase is separated off and washed with water, dried and filtered and the solvent is carefully distilled off from the filtrate under reduced pressure and at a moderately elevated temperature (subjected to "incipient distillation").

The active compounds are well tolerated by plants, have a favorable level of toxicity to warm-blooded animals, and can be used for combating arthropod pests, especially insects and acarids, which are encountered in agriculture, in forestry, in the protection of stored products and of materials, and in the hygiene field. They are active against normally sensitive and resistant species and against all or some stages of development. The above-mentioned pests include:

from the class of the Isopoda, for example Cniscus asellus, Armadillidium vulgare and Porcellio scaber;

from the class of the Diplopoda, for example Blaniulus guttulatus;

from the class of the Chilopoda, for example Geophilus carpophagus and Scutigera spec.;

from the class of the Symphyla, for example Scutigerella immaculate;

from the order of the Thysanura, for example Lepisma saccharina;

from the order of the Collembola, for example Onychiurus armatus;

from the order of the Orthoptera, for example Blatta orientalis, Periplaneta americana, Leucophaea maderae, Blattella germanica, Acheta domesticus, Gryllotalpa spp., Locusta migratoria migratorioides, Melanoplus differentialis and Schistocerca gregaria;

from the order of the Dermaptera, for example Forficula auricularia;

from the order of the Isoptera, for example Reticulitermes spp.;

from the order of Anoplura, for example Phylloxera vastatrix, Pemphigus spp., pediculus humanus corporis, Haematophinus spp. and Linognathus spp.;

from the order of the Mallophaga, for example Trichlodectes spp. and Damalinea spp.;

from the order of the Thysanoptera, for example Hercinothrips femoralis and Thrips tabaci;

from the order of the Heteroptera, for example Eurygaster spp., Dysdercus intermedius, Piesma quadrata, Cimex lectularius, Rhodnius prolixus and Triatoma spp.;

from the order of the Homoptera, for example Aleurodes brassicae, Bemisia tabaci, Trialeurodes vaporariorum, Aphis gossypii, Brevicoryne brassicae, Cryptomyzus ribis, Doralis fabae, Doralis pomi, Eriosoma lanigerum, Hyalopterus arundinis, Macrosiphum avenae, Myzus spp., Phorodon humuli, Rhopalosiphum padi, Empoasca spp., Euscelis bilobatus, Nephotettix cincticeps, Lecanium corni, Saissetia oleae, Laodelphax striatellus, Nilaparvata lugens, Aonidiella aurantii, Aspidiotus hederae, Pseudococcus spp. and Psylla spp.;

from the order of the Lepidoptera, for example Pectinophora gossypiella, Bupalus piniarius, Cheimatobia brumata, Lithocolletis blancardella, Hyponomeuta padella, Plutella maculipennis, Malacosoma neustria, Euproctis chrysorrhoea, Lymantria spp., Bucculatrix thurberiella, Phyllocnistis citrella, Agrotis spp., Euxoa spp., Feltia spp., Earias insulana, Heliothis spp., Laphygma exigua, Mamestra brassicae, Panolis flammea, Prodenia litura, Spodoptera spp., Trichoplusia ni, Carpocapsa pomonella, Pieris spp., Chilo spp., Pyrausta nubilalis, Ephestia kuehniella, Galleria mellonella, Cacoecia podana, Capua reticulana, Choristoneura fumiferana, Cylsia ambiguella, Homona magnanima and Tortrix viridana;

from the order of the Coleoptera, for example Anobium punctatum, Rhizopertha dominica, Bruchidius obtectus, Acanthoscelides obtectus, Hylotrupes bajulus, Agelastica alni, Leptinotarsa decemlineata, Phaedon cochleariae, Diabrotica spp., Psylliodes chrysocephala, Epilachna varivestis, Atomaria spp., Oryzaephilus surinamensis, Anthonomus spp., Sitophilus spp., Otiorrhynchus sulcatus, Cosmopolites sordidus, Ceuthorrhynchus assimilis, Hypera postica, Dermestes spp., Trogoderma spp., Anthrenus spp., Attagenus spp., Lyctus spp., Meligethes aeneus, Ptinus spp., Niptus hololeucus, Gibbium psylloides, Tribolium spp., Tenebrio molitor, Agriotes spp., Conoderus spp., Melolontha melolontha, Amphimallon solstitialis and Costelytra zealandica;

from the order of the Hymenoptera, for example Diprion spp., Hoplocampa spp., Lasius spp., Monomorium pharaonis and Vespa spp.,

from the order of the Diptera, for example Aedes spp., Anopheles spp., Culex spp., Drosophila melanogaster, Musca spp., Fannia spp., Calliphora erythrocephala, Lucilia spp., Chrysomyia spp., Cuterebra spp., Gastrophilus spp., Hyppobosca spp., Stomoxys spp., Oestrus spp., Hypoderma spp., Tabanus spp., Tannia spp., Bibio hortulanus, Oscinella frit, Phorbia spp., Pegomyia hyoscyami, Ceratitis capitate, Dacus oleae and Tipula paludosa;

from the order of the Siphonaptera, for example Xenopsylla cheopis and Ceratophyllus spp.;

from the class of the Arachnida, for example Scorpio maurus and Latrodectus mactans;

from the order of the Acarina, for example Acarus siro, Argas spp., Ornithodoros spp., Dermanyssus gallinae, Eriophyes ribis, Phyllocoptruta oleivora, Boophilus spp., Rhipicephalus spp., Amblyomma spp., Hyalomma spp., Ixodes spp., Psoroptes spp., Chorioptes spp., Sarcoptes spp., Tarsonemus spp., Bryobia praetiosa, Panonychus spp. and Tetranychus spp..

The active compounds can be converted into the customary formulations, such as solutions, emulsions, suspensions, powders, dusting agents, foams, pastes, soluble powders, granules, aerosols, suspension-emulsion concentrates, seed-treatment powders, natural and synthetic materials impregnated with active compound, very fine capsules in polymeric substances, coating compositions for use on seed, and formulations used with burning equipment, such as fumigating cartridges, fumigating cans and fumigating coils, as well as ULV cold mist and warm mist formulations.

These formulations may be produced in known manner, for example by mixing the active compounds with extenders, that is to say liquid or liquefied gaseous or solid diluents or carriers, optionally with the use of surface-active agents, that is to say emulsifying agents and/or dispersing agents and/or foam-forming agents. In the case of the use of water as an extender, organic solvents can, for example, also be used as auxiliary solvents.

As liquid diluents or carriers, especially solvents, there are suitable in the main, aromatic hydrocarbons, such as xylene, toluene or alkyl naphthalenes, chlorinated aromatic or chlorinated aliphatic hydrocarbons, such as chlorobenzenes, chloroethylenes or methylene chloride, aliphatic or alicyclic hydrocarbons, such as cyclohexane or paraffins, for example mineral oil fractions, alcohols, such as butanol or glycol as well as their ethers and esters, ketones, such as acetone, methyl ethyl ketone, methyl isobutyl ketone or cyclohexanone, or strongly polar solvents, such as dimethylformamide and dimethylsulphoxide, as well as water.

By liquefied gaseous diluents or carriers are meant liquids which would be gaseous at normal temperature and under normal pressure, for example aerosol propellants, such as halogenated hydrocarbons as well as butane, propane, nitrogen and carbon dioxide.

As solid carriers there may be used ground natural minerals, such as kaolins, clays, talc, chalk, quartz, attapulgite, montmorillonite or diatomaceous earth, and ground synthetic minerals, such as highly-dispersed silicic acid, alumina and silicates. As solid carriers for granules there may be used crushed and fractionated natural rocks such as calcite, marble, pumice, sepiolite and dolomite, as well as synthetic granules of inorganic and organic meals, and granules of organic material such as sawdust, coconut shells, corn cobs and tobacco stalks.

As emulsifying and/or foam-forming agents there may be used non-ionic and anionic emulsifiers, such as polyoxyethylene-fatty acid esters, polyoxyethylene-fatty alcohol ethers, for example alkylaryl polyglycol ethers, alkyl sulphonates, alkyl sulphates, aryl sulphonates as well as albumin hydrolysis products. Dispersing agents include, for example, lignin sulphite waste liquors and methylcellulose.

Adhesives such as carboxymethylcellulose and natural and synthetic polymers in the form of powders, granules or latices, such as gum arabic, polyvinyl alcohol and polyvinyl acetate, can be used in the formulations.

It is possible to use colorants such as inorganic pigments, for example iron oxide, titanium oxide and Prussian Blue, and organic dyestuffs, such as alizarin dyestuffs, azo dyestuffs or metal phthalocyanine dyestuffs, and trace nutrients, such as salts of iron, manganese, boron, copper, cobalt, molybdenum and zinc.

The formulations in general contain from 0.1 to 95 percent by weight of active compound, preferably from 0.5 to 90 percent by weight.

The active compounds according to the invention may be used in the form of their formulations of the types that are commercially available or in the use forms prepared from these formulations.

The active compound content of the use forms prepared from the formulations of the types that are commercially available can vary within wide ranges. The active compound concentration of the use forms can be from 0.0000001 to 100% by weight of active compound, preferably from 0.0001 to 1% by weight.

The compounds may be employed in a customary manner appropriate for the particular use forms.

When used against pests harmful to health and pests of stored products, the active compounds are distinguished by an excellent residual activity on wood and clay as well as a good stability to alkali on limed substrates.

The active compounds according to the invention are also suitable for combating ectoparasites and endoparasites in the field of veterinary medicine.

In the veterinary field, the active compounds according to the invention may be used in a known manner, such as orally in the form of, for example, tablets, capsules, drenches and granules; dermally by means of, for example, dipping, spraying, pouring-on, spotting-on and powdering; and parenterally, for example by means of injections.

The present invention also provides pesticidal compositions containing as active ingredient a compound of the present invention in admixture with a solid or liquefied gaseous diluent or carrier or in admixture with a liquid diluent or carrier containing a surface-active agent.

The present invention also provides a method of combating pests (in particular arthropods and especially insects or acarids) which comprises applying to the pests, or to a habitat thereof, a compound of the present invention alone or in the form of a composition containing as active ingredient a compound of the present invention in admixture with a diluent or carrier.

The present invention also provides a method of freeing or protecting domesticated animals from parasites which comprises applying to said animals a compound according to the present invention, in admixture with a diluent or carrier.

The present invention further provides crops protected from damage by pests by being grown in areas in which immediately prior to and/or during the time of the growing a compound of the present invention was applied alone or in admixture with a diluent or carrier.

It will be seen that the usual methods of providing a harvested crop may be improved by the present invention.

The present invention further provides domesticated animals whenever freed or protected from parasites by the application to said animals of a compound according to the present invention, in admixture with a diluent or carrier.

PREPARATIVE EXAMPLES Example 1 ##STR7##

5.05 g (0.0232 mol) of 3-(4-fluoro-phenoxy)-benzyl alcohol and 3.72 g (0.0232 mol) of 2,2,3,3-tetramethylcyclopropanecarboxylic acid chloride were dissolved in 100 ml of anhydrous toluene, and 2.3 g of pyridine, dissolved in 50 ml of anhydrous toluene, were added dropwise at 20°-25° C., while stirring. The reaction mixture was then stirred for a further 3 hours at 25° C. It was poured into 150 ml of water, to which 10 ml of concentrated hydrochloric acid had been added, and the organic phase was separated off and washed again with 100 ml of water. The toluene phase was then dried over sodium sulphate and the solvent was distilled off under a waterpump vacuum. Last residues of solvent were removed by brief incipient distillation at a bath temperature of 60° C./1 mm Hg. 6.5 g (81.9% of theory) of 2,2,3,3-tetramethyl-cyclopropanecarboxylic acid 3-(4-fluorophenoxy)-benzyl ester were obtained as a yellow oil with a refractive index n_(D) ²⁰ of 1.5348.

Example 2

The following compound was obtained analogously to Example 1: ##STR8##

Refractive index n_(D) ²⁴ : 1.5340

Example 3 ##STR9##

0.1 mol of tetramethylcyclopropanecarboxylic acid chloride and 0.1 mol of pentafluorobenzyl alcohol were slowly heated to 100° C., without a solvent, until the evolution of gas had ended. The reaction mixture was then distilled in a bulb tube. Yield: 95%, boiling point: 150° C./2 mm Hg.

Example 4 ##STR10##

5 g (0.0232 mol) of 3-phenoxy-4-fluoro-benzaldehyde and 3.72 g (0.0232 mol) of 2,2,3,3-tetramethylcyclopropanecarboxylic acid chloride were together added dropwise to a mixture of 1.8 g of sodium cyanide, 2.7 ml of water, 100 ml of n-hexane and 0.6 g of tetrabutylammonium bromide at 20°-25° C., while stirring, and the mixture was then stirred at 20°-25° C. for 4 hours. 300 ml of toluene were then added to the reaction mixture and the mixture was extracted twice by shaking with 300 ml of water each time. The organic phase was separated off and dried over magnesium sulphate and the solvent was distilled off under a waterpump vacuum. Last residues of solvent were removed by brief incipient distillation at a bath temperature of 60° C./1 mm Hg. 67 g (78.7% of theory) of 2,2,3,3-tetramethylcyclopropanecarboxylic acid α-cyano-3-phenoxy-4-fluoro-benzyl ester were obtained as a yellow oil with a refractive index n_(D) ²⁴ of 1.5732.

Example 5

The following compound was obtained analogously to Example 4. ##STR11##

Refractive index n_(D) ²⁰ : 1.5480.

The pesticidal activity of the compounds of this invention is illustrated by the following biological examples wherein the compounds according to the present invention are each identified by the number (given in brackets) of the corresponding preparative example.

EXAMPLE 6 LT₁₀₀ test for Diptera

Test insects: Aedes aegypti

Number of test insects: 25

Solvent: Acetone

The active compound was dissolved in the solvent at a rate of 2 g per liter. The solution so obtained was diluted with further solvent to the desired lower concentrations.

2.5 ml of the solution of active compound were pipetted into a Petri dish. On the bottom of the Petri dish there was a filter paper with a diameter of about 9.5 cm. The Petri dish remained uncovered until the solvent had completely evaporated. The amount of active compound per square meter of filter paper varied with the concentration of the solution of active compound. The stated number of test insects was then placed in the Petri dish and the dish was covered with a glass lid.

The condition of the test insects was continuously observed. The time which was necessary for 100% "knockdown" as determined.

In this test, for example, the following compounds showed a superior action compared with the prior art: (2) and (4).

Example 7

Test insects: Blatta orientalis

Number of test insects: 10

Solvent: Acetone

The active compound was taken up in the solvent at a rate of 2 g per liter. The solution so obtained was diluted with further solvent to the desired concentrations.

2.5 ml of the solution of the active compound were pipetted into a Petri dish. On the bottom of the Petri dish there was a filter paper with a diameter of about 9.5 cm. The Petri dish remained uncovered until the solvent had completely evaporated. The amount of active compound per square meter of filter paper varied with the concentration of the solution of active compound. The stated number of test insects was then placed in the Petri dish and the dish was covered with a glass lid.

The condition of the test insects was observed 3 days after the commencement of the experiments. The destruction, in %, was determined. 100% denoted that all of the test insects had been killed; 0% denoted that none of the test insects had been killed.

In this test, for example, the following compounds showed a superior action compared with the prior art: (2) and (4).

Example 8 Laphygma test

Solvent: 3 parts by weight of acetone

Emulsifier: 1 part by weight of alkylaryl polyglycol ether

To produce a suitable preparation of active compound, 1 part by weight of the active compound was mixed with the stated amount of solvent and the stated amount of emulsifier and the concentrate was diluted with water to the desired concentration.

Cabbage leaves (Brassica oleracea) were treated by being dipped into the preparation of active compound of the desired concentration and were infested with caterpillars of the owlet moth (Laphygma frugiperda), as long as the leaves were still moist.

After the specified periods of time, the destruction in % was determined. 100% meant that all of the caterpillars had been killed whereas 0% indicated that none of the caterpillars had been killed.

In this test, for example, the following compound showed a superior activity compared with the prior art: (4).

Example 9 Tetranychus test (resistant)

Solvent: 3 parts by weight of acetone

Emulsifier: 1 part by weight of alkylaryl polyglycol ether

To produce a suitable preparation of active compound, 1 part by weight of the active compound was mixed with the stated amount of solvent and the stated amount of emulsifier and the concentrate was diluted with water to the desired concentration.

Bean plants (Phaseolus vulgaris) which were heavily infested with the two-spotted spider mite (Tetranychus urticae) in all stages of development were treated by being dipped into the preparation of the active compound.

After the specified periods of time, the degree of destruction was determined as a percentage: 100% meant that all of the spider mites were killed whereas 0% meant that none of the spider mites were killed.

In this test, for example, the following compounds showed a superior activity compared with the prior art: (2) and (4).

EXAMPLE 10 Test with Boophilus microplus resistant

Solvent:

35 parts by weight of ethylene glycol monomethyl ester

35 parts by weight of nonylphenol polyglycol ether

To produce a suitable preparation of active compound, three parts by weight of active compound were mixed with seven parts by weight of the solvent mixture indicated above, and the concentrate thus obtained was diluted with water to the desired concentration.

10 Adult Boophilus microplus res.were immersed for 1 minute in the active compound preparation to be tested. After transfer to plastic beakers and storage in a climatically controlled chamber, the degree of destruction was determined.

In this test, for example, the following compounds showed a superior activity compared with the prior art: (2) and (4).

EXAMPLE 11 Test with Lucilia cuprina res. larvae

Emulsifier:

35 parts by weight of ethylene glycol monomethyl ether

35 parts by weight of nonylphenol polyglycol ether

To produce a suitable preparation of active compound, three parts by weight of active compound were mixed with seven parts by weight of the above-mentioned solvent mixture and the concentrate thus obtained was diluted with water to the particular desired concentration.

About 20 Lucilia cuprina res. larvae were introduced into a test tube which contained approximately 1 cm³ of horse meat and 0.5 ml of the preparation of active compound. After 24 hours, the degree of destruction was determined.

In this test, for example, the following compounds showed a superior activity compared with the prior art: (2) and (4).

Example 12 Phaedon larvae test

Solvent: 3 parts by weight of acetone

Emulsifier: 1 part by weight of alkylaryl polyglycol ether

To produce a suitable preparation of active compound, 1 part by weight of the active compound was mixed with the stated amount of solvent containing the stated amount of emulsifier and the concentrate was diluted with water to the desired concentration.

Cabbage leaves (Brassica oleracea) were treated by being dipped into the preparation of the active compound and were infested with mustard beetle larvae (Phaedon cochleariae), as long as the leaves were still wet.

After the specified periods of time, the degree of destruction was determined in %: 100% meant that all of the beetle larvae had been killed whereas 0% meant that none of the beetle larvae had been killed.

In this test, for example, the following compound showed a superior activity compared with the prior art: (2)

Example 13 Myzus test (contact action)

Solvent: 3 parts by weight of acetone

Emulsifier: 1 part by weight of alkylaryl polyglycol ether

To produce a suitable preparation of active compound, 1 part by weight of the active compound was mixed with the stated amount of solvent containing the stated amount of emulsifier and the concentrate was diluted with water to the desired concentration.

Cabbage plants (Brassica oleracea) which had been heavily infested with peach aphids (Myzus persicae) were treated by being dipped into the preparation of active compound of the desired concentration.

After the specified periods of time, the degree of destruction was determined as a percentage: 100% meant that all of the aphids were killed whereas 0% meant that none of the aphids were killed.

In this test, for example, the following compound showed a superior activity compared with the prior art: (4).

It will be appreciated that the instant specification and examples are set forth by way of illustration and not limitation, and that various modifications and changes may be made without departing from the spirit and scope of the present invention. 

We claim:
 1. A 2,2,3,3-tetramethylcyclopropane-1-carboxylic acid fluorine-substituted-benzyl ester of the formula ##STR12## in which R¹ is hydrogen, cyano, or alkyl, alkenyl or alkynyl each with up to 4 carbon atoms, andR² is a phenyl radical which is substituted by halogen and/or by optionally halogen-substituted phenoxy, with the proviso that the radical R² in total contains at least one fluorine substituent.
 2. A compound according to claim 1, in whichR¹ is hydrogen or cyano, and R² is pentafluorophenyl, 4-fluoro-3-phenoxyphenyl, 3-(4-fluoro-phenoxy)-phenyl or 4-fluoro-3-(4-fluoro-phenoxy)-phenyl.
 3. A compound according to claim 1, wherein such compound is 2,2,3,3-tetramethyl-cyclopropanecarboxylic acid 3-(4-fluorophenoxy)-benzyl ester of the formula ##STR13##
 4. A compound according to claim 1, wherein such compound is 2,2,3,3-tetramethyl-cyclopropanecarboxylic acid 3-phenoxy-4-fluoro-benzyl ester of the formula ##STR14##
 5. A compound according to claim 1, wherein such compound is 2,2,3,3-tetramethyl-cyclopropanecarboxylic acid pentafluorobenzyl ester of the formula ##STR15##
 6. A compound according to claim 1, wherein such compound is 2,2,3,3-tetramethyl-cyclopropanecarboxylic acid α-cyano-3-phenoxy-4-fluoro-benzyl ester of the formula ##STR16##
 7. A compound according to claim 1, wherein such compound is 2,2,3,3-tetramethyl-cyclopropanecarboxylic acid α-cyano-3-(4-fluorophenoxy)-benzyl ester of the formula ##STR17##
 8. An insecticidal or acaricidal composition comprising as active ingredient an insecticidally or acaricidally effective amount of a compound according to claim 1 in admixture with a diluent.
 9. A method of combating insects or acarids comprising applying to the insects or acarids or to a habitat thereof, an insecticidally or acaricidally effective amount of a compound according to claim
 1. 10. The method according to claim 9, wherein such compound is2,2,3,3-tetramethyl-cyclopropanecarboxylic acid 3-(4-fluorophenoxy)-benzyl ester, 2,2,3,3-tetramethyl-cyclopropanecarboxylic acid 3-phenoxy-4-fluoro-benzyl ester, 2,2,3,3-tetramethyl-cyclopropanecarboxylic acid pentafluorobenzyl ester, 2,2,3,3-tetramethyl-cyclopropanecarboxylic acid α-cyano-3-phenoxy-4-fluoro-benzyl ester, or 2,2,3,3-tetramethyl-cyclopropanecarboxylic acid α-cyano-3-(4-fluorophenoxy)-benzyl ester. 